[Servers] Investigate some flaky Interop tests

[pr-benchmarks]

We have some Interop tests that are flaky. There should be some recent failures to get logs from, but it's possible some of them have been purged due to the retention policy (if that's the case, we can close this and see if it falls off the flaky test radar for now).

Metadata

Affected Tests

Project	Type	Method
Interop.FunctionalTests	Interop.FunctionalTests.HttpClientHttp2InteropTests	Settings_MaxHeaderListSize_Server
Interop.FunctionalTests	Interop.FunctionalTests.HttpClientHttp2InteropTests	RequestHeaders_MultipleFrames_Accepted
Interop.FunctionalTests	Interop.FunctionalTests.HttpClientHttp2InteropTests	Settings_MaxConcurrentStreamsPost_Server
Interop.FunctionalTests	Interop.FunctionalTests.HttpClientHttp2InteropTests	Settings_MaxConcurrentStreamsGet_Server

[Tratcher]

Known issue for Settings_MaxHeaderListSize_Server and RequestHeaders_MultipleFrames_Accepted: dotnet/runtime#860

[BrennanConroy]

We believe this has been fixed, the Runtime issue was closed. These tests are likely ready for unquarantine.